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On Site Guide intelligence

Pirform's intelligence incorporates guidance from the IET's On-Site Guide, specifically Table 7.1(ii). Read more here.

Info

The following applies to flat twin and earth cables. This is wiring type AF in Pirform:

The Pirform wiring type selector showing the flat twin and earth cable type

Ring Final Circuits

Note

For ring final circuits, Pirform provides no cable-sizing guidance other than checking for compliance against the IET's On-Site Guide, as below. If a circuit does not match any of these standard ring final circuit criteria, the circuit might still comply (for instance, when your circuit is not wired in flat twin and earth). Refer to Regulation 433.1.204 for details.

The following ring final circuits are recognised as valid by our cable-sizing rules.

Rating Standard Live CPC Reference Methods TN-S
30 mA RCD		 TN-S
No RCD		 TN-C-S
30 mA RCD		 TN-C-S
No RCD
30 3036 2.5 1.5 100,102,A,C 106 41zs 106 106
30 3036 4 1.5 100,102,A,101,103,C 171 48 171 138zs
32 CB or RCBO B/C/D 2.5 1.5 100,102,A,C 106 96zs 106 106
32 CB or RCBO B/C/D 2.5 1.5 100,102,A,C 106 NPzs 106 56zs
32 CB or RCBO B/C/D 2.5 1.5 100,102,A,C 106 NPzs 106 NPzs
32 88-2 (60269-2) 2.5 1.5 100,102,A,C 106vd 32zs 106vd 106vd
32 88-2 (60269-2) 4 1.5 100,101,102,103,A,C 171 38zs 106vd 127zs
32 88-3 2.5 1.5 100,102,A,C 106vd 19ad 106 95zs
32 88-3 4 1.5 100,101,102,103,A,C 171 22zs 171 112zs
32 CB or RCBO B/C/D 4 1.5 100,101,102,103,A,C 171vd 114zs 171vd 171vd
32 CB or RCBO B/C/D 4 1.5 100,101,102,103,A,C 171vd NPzs 171vd 66zs
32 CB or RCBO B/C/D 4 1.5 100,101,102,103,A,C 171vd NPzs 171vd NPzs

Lighting Circuits

The following lighting circuits are recognised as valid by our cable-sizing rules.

Rating Standard Live CPC Reference Methods TN-S
30 mA RCD		 TN-S
No RCD		 TN-C-S
30 mA RCD		 TN-C-S
No RCD
5 3036 1 1 100,101,102,103,A,C 68 68 68 68
5 3036 1.5 1 100,101,102,103,A,C 106 106 106 106
5 88-3 1 1 100,101,102,103,A,C 68 68 68 68
5 88-3 1.5 1 100,101,102,103,A,C 106 106 106 106
6 CB or RCBO B/C/D 1 1 100,101,102,103,A,C 68 68 68 68
6 CB or RCBO B/C/D 1 1 100,101,102,103,A,C 68 65zs 68 68
6 CB or RCBO B/C/D 1 1 100,101,102,103,A,C 68 23zs 68 34zs
6 88-2 (60269-2) 1 1 100,101,102,103,A,C 68 68 68 68
6 CB or RCBO B/C/D 1.5 1 100,101,102,103,A,C 106 106 106 106
6 CB or RCBO B/C/D 1.5 1 100,101,102,103,A,C 106 78zs 106 91zs
6 CB or RCBO B/C/D 1.5 1 100,101,102,103,A,C 106 28zs 106 41zs
6 88-2 (60269-2) 1.5 1 100,101,102,103,A,C 106 106 106 106
10 CB or RCBO B/C/D 1 1 100,101,102,A,C 42vd 42vd 42vd 42vd
10 CB or RCBO B/C/D 1 1 100,101,102,A,C 42vd 32zs 42vd 42vd
10 CB or RCBO B/C/D 1 1 100,101,102,A,C 42vd 23zs 42vd 34zs
10 CB or RCBO B/C/D 1.5 1 100,101,102,A,C 65vd 65vd 65vd 65vd
10 CB or RCBO B/C/D 1.5 1 100,101,102,A,C 65vd 38zs 65vd 51zs
10 CB or RCBO B/C/D 1.5 1 100,101,102,A,C 65vd 28zs 65vd 41zs
10 88-2 (60269-2) 1 1 100,101,102,A,C 42 42 42 42
10 88-2 (60269-2) 1.5 1 100,101,102,A,C 65 65 65 65
16 CB or RCBO B/C/D 1.5 1 100,102,C 34 34 34 34
16 CB or RCBO B/C/D 1.5 1 100,102,C 34 15sc 34 28zs
16 CB or RCBO B/C/D 1.5 1 100,102,C 34 NPad 34 9zs
16 CB or RCBO B/C/D 2.5 1.5 100,101,102,A,C 49 49 49 49
16 CB or RCBO B/C/D 2.5 1.5 100,101,102,A,C 49 24zs 49 44zs
16 CB or RCBO B/C/D 2.5 1.5 100,101,102,A,C 49 NPad 49 14zs
16 88-2 (60269-2) 1.5 1 100,102,C 20 20 20 20
16 88-2 (60269-2) 2.5 1.5 100,101,102,A,C 49 49 49 49
16 88-3 1.5 1 100,102,C 34 34 34 34
16 88-3 2.5 1.5 100,101,102,A,C 34 34 34 34

Radial Final Circuits

The following radial final circuits are recognised as valid by our cable-sizing rules.

Rating Standard Live CPC Reference Methods TN-S
30 mA RCD		 TN-S
No RCD		 TN-C-S
30 mA RCD		 TN-C-S
No RCD
5 3036 1 1 100,101,102,103,A,C 56 56 56 56
5 88-3 1 1 100,101,102,103,A,C 56 56 56 56
5 3036 1.5 1 100,101,102,103,A,C 88 88 88 88
5 88-3 1.5 1 100,101,102,103,A,C 88 88 88 88
6 CB or RCBO B/C/D 1 1 100,101,102,103,A,C 56 56 56 56
6 CB or RCBO B/C/D 1 1 100,101,102,103,A,C 56 56 56 56
6 CB or RCBO B/C/D 1 1 100,101,102,103,A,C 56 23zs 56 33zs
6 88-2 (60269-2) 1 1 100,101,102,103,A,C 56 56 56 56
6 88-2 (60269-2) 1.5 1 100,101,102,103,A,C 88 88 88 88
6 CB or RCBO B/C/D 1.5 1 100,101,102,103,A,C 88 88 88 88
6 CB or RCBO B/C/D 1.5 1 100,101,102,103,A,C 88 78zs 88 88
6 CB or RCBO B/C/D 1.5 1 100,101,102,103,A,C 88 28zs 88 40zs
10 CB or RCBO B/C/D 1 1 100,101,102,A,C 35 35 35 36
10 CB or RCBO B/C/D 1 1 100,101,102,A,C 35 31zs 35 36
10 CB or RCBO B/C/D 1 1 100,101,102,A,C 35 6zs 18ad 17zs
10 CB or RCBO B/C/D 1.5 1 100,101,102,103,A,C 52 52 52 52
10 CB or RCBO B/C/D 1.5 1 100,101,102,103,A,C 52 38zs 52 50zs
10 CB or RCBO B/C/D 1.5 1 100,101,102,103,A,C 10ad 8zs 52 20zs
10 88-2 (60269-2) 1 1 100,101,102,A,C 35 35 35 35
10 88-2 (60269-2) 1.5 1 100,101,102,103,A,C 52 52 52 52
15 3036 1 1 NP NP NP NP
15 3036 1.5 1 NP NP NP NP
15 3036 2.5 1.5 100,102,C 47 47 47 47
15 3036 4 1.5 100,101,102,A,C 76 76 76 76
16 CB or RCBO B/C/D 1 1 C 18 18 18 18
16 CB or RCBO B/C/D 1 1 C 18 13zs 18 13
16 CB or RCBO B/C/D 1 1 C 18 7 8ad NPad
16 88-2 (60269-2) 1.5 1 100,102,C 27 27 27 27
16 88-2 (60269-2) 2.5 1.5 100,101,102,A,C 45 45 45 45
16 88-2 (60269-2) 4 1.5 100,101,102,103,A,C 74 74 74 74
16 88-3 1.5 1 100,102,C 27 27 27 27
16 88-3 2.5 1.5 100,101,102,A,C 45 45 45 45
16 88-3 4 1.5 100,101,102,103,A,C 74 74 74 74
16 CB or RCBO B/C/D 1.5 1 100,102,C 27 27 27 27
16 CB or RCBO B/C/D 1.5 1 100,102,C 27 15zs 27 27
16 CB or RCBO B/C/D 1.5 1 100,102,C 27 NPad 27 9zs
16 CB or RCBO B/C/D 2.5 1.5 100,101,102,A,C 45 45 45 45
16 CB or RCBO B/C/D 2.5 1.5 100,101,102,A,C 45 24zs 45 43zs
16 CB or RCBO B/C/D 2.5 1.5 100,101,102,A,C 45 NPzs 45 14zs
16 CB or RCBO B/C/D 4 1.5 100,101,102,103,A,C 69 32ad 69 69
16 CB or RCBO B/C/D 4 1.5 100,101,102,103,A,C 32ad 16zs 54ad 36zs
16 CB or RCBO B/C/D 4 1.5 100,101,102,103,A,C NPad NPad 18ad 9zs
20 3036 2.5 1.5 100,101,102,A NP NP NP NP
20 CB or RCBO B/C/D 2.5 1.5 100,102,A,C 42 42 42 42
20 CB or RCBO B/C/D 2.5 1.5 100,102,A,C 42 12zs 42 31zs
20 CB or RCBO B/C/D 2.5 1.5 100,102,A,C 42 NPad 42 8zs
20 3036 4 1.5 C 69 43zs 73 66zs
20 CB or RCBO B/C/D 4 1.5 100,101,102,A,C 69 69 69 69
20 CB or RCBO B/C/D 4 1.5 100,101,102,A,C 69 14zs 69 36zs
20 CB or RCBO B/C/D 4 1.5 100,101,102,A,C 69 NPad 69 9zs
20 3036 6 2.5 100,102,A,C 105 69zs 105 105
20 CB or RCBO B/C/D 6 2.5 100,101,102,103,A,C 105 107 105 105
20 CB or RCBO B/C/D 6 2.5 100,101,102,103,A,C 105 23zs 105 58zs
20 CB or RCBO B/C/D 6 2.5 100,101,102,103,A,C 105 NPzs 105 15zs
20 88-2 (60269-2) 2.5 1.5 100,102,A,C 42 42 42 42
20 88-2 (60269-2) 4 1.5 100,101,102,A,C 69 43zs 69 66zs
20 88-2 (60269-2) 6 2.5 100,101,102,103,A,C 105 69zs 105 105
20 88-3 2.5 1.5 100,102,A,C 42 42 42 42
20 88-3 4 1.5 100,101,102,A,C 69 56zs 69 69
20 88-3 6 2.5 100,101,102,103,A,C 105 89zs 105 105
25 CB or RCBO B/C/D 2.5 1.5 C 33 33 33 33
25 CB or RCBO B/C/D 2.5 1.5 C 33 2zs 33 22zs
25 CB or RCBO B/C/D 2.5 1.5 C 33 NPad 33 4zs
25 CB or RCBO B/C/D 4 1.5 100,102,A,C 55 47zs 55 55
25 CB or RCBO B/C/D 4 1.5 100,102,A,C 55 3zs 55 26sc
25 CB or RCBO B/C/D 4 1.5 100,102,A,C 55 NPad 55 4zs
25 CB or RCBO B/C/D 6 2.5 100,101,102,A,C 83 75zs 83 83
25 CB or RCBO B/C/D 6 2.5 100,101,102,A,C 83 5zs 83 43zs
25 CB or RCBO B/C/D 6 2.5 100,101,102,A,C 83 NPzs 83 7zs
25 88-2 (60269-2) 2.5 1.5 C 31 20zs 31 31
25 88-2 (60269-2) 4 1.5 100,102,A,C 53 24zs 53 46zs
25 88-2 (60269-2) 6 2.5 100,101,102,A,C 82 38zs 82 76zs
30 3036 4 1.5 NP NP NP NP
30 3036 6 2.5 C 66 19zs 66 54zs
30 3036 10 4 100,102,A,C 110 31zs 110 89zs
32 CB or RCBO B/C/D 4 1.5 C 43 28zs 43 43
32 CB or RCBO B/C/D 4 1.5 C 43 NPad 43 16zs
32 CB or RCBO B/C/D 4 1.5 C 43 NPad 43 NPad
32 CB or RCBO B/C/D 6 2.5 100,102,A,C 63 45zs 63 63
32 CB or RCBO B/C/D 6 2.5 100,102,A,C 63 NPzs 63 26zs
32 CB or RCBO B/C/D 6 2.5 100,102,A,C 63 NPzs 63 NPzs
32 CB or RCBO B/C/D 10 4 100,101,102,103,A,C 105 74zs 105 105zs
32 CB or RCBO B/C/D 10 4 100,101,102,103,A,C 105 NPad 105 42zs
32 CB or RCBO B/C/D 10 4 100,101,102,103,A,C 105 NPzs 105 NPsc
32 88-2 (60269-2) 4 1.5 C 43 9zs 43 31zs
32 88-2 (60269-2) 6 2.5 100,102,A,C 63 15zs 63 50zs
32 88-2 (60269-2) 10 4 100,101,102,103,A,C 105 24zs 105 82zs
32 88-3 4 1.5 C 43 5zs 43 27zs
32 88-3 6 2.5 100,102,A,C 63 8zs 63 44zs
32 88-3 10 4 100,101,102,103,A,C 105 14zs 105 72zs
40 CB or RCBO B/C/D 6 2.5 C 46 23zs 46 46
40 CB or RCBO B/C/D 6 2.5 C 46 NPzs 46 15zs
40 CB or RCBO B/C/D 6 2.5 C 46 NPzs 46 NPzs
40 CB or RCBO B/C/D 10 4 100,102,A,C 72 37zs 72 72
40 CB or RCBO B/C/D 10 4 100,102,A,C 72 NPzs 72 25zs
40 CB or RCBO B/C/D 10 4 100,102,A,C 72 NPzs 72 NPzs
40 CB or RCBO B/C/D 16 6 100,101,102,103,A,C 118 57zs 118 118
40 CB or RCBO B/C/D 16 6 100,101,102,103,A,C 118 NPzs 118 39zs
40 CB or RCBO B/C/D 16 6 100,101,102,103,A,C 118 NPzs 118 NPad
40 88-2 (60269-2) 6 2.5 C 46 NPzs 46 32zs
40 88-2 (60269-2) 10 4 100,102,A,C 72 NPzs 72 52zs
40 88-2 (60269-2) 16 6 100,101,102,103,A,C 118 NPzs 118 79zs

Glossary

The following abbreviations are used in the tables above:

  • CB: Circuit breaker
  • RCBO: Residual current circuit breaker with overcurrent protection
  • TN-S: Terra neutral - separate
  • TN-C-S: Terra neutral - combined and separate
  • RCD: Residual current device
  • vd: Voltage drop
  • ad: Adiabatic limit
  • zs: Earth fault loop impedance
  • sc: Line to neutral
  • NP: Not permitted
  • NPvd: Not permitted (prohibiting factor: voltage drop)
  • NPad: Not permitted (prohibiting factor: adiabatic limit)
  • NPzs: Not permitted (prohibiting factor: earth fault loop impedance)
  • NPsc: Not permitted (prohibiting factor: line to neutral)